London's top stocks are expected to open largely flat as investors take a breather following the previous sessions gains.Costa Coffee owner Whitbread has offered to buy Eastern European coffee shop operator CoffeeHeaven for about £36m. The recommended offer of 24 pence in cash represents a premium of around 25% to the closing price of 19.25 pence per CoffeeHeaven share on 11 June 2009, being the last business day prior to the announcement by the AIM-listed company that it is in early stage takeover talks. Serco is confident enough about prospects to repeat forecasts for 2009 ahead of meetings with analysts prior to its financial year end on 31 December. The outsourcing group predicts double-digit revenue growth this year and a 30 basis point increase in adjusted pre-tax profit margin, excluding SI International which should increase growth by some 10%.National Express has received 90.47% acceptances for its £360m rights issue, the bus and trains operator confirmed Tuesday. Shareholders owning more than 323m shares subscribed for the fully underwritten 7 for 3 cash call at 105p a share.Lloyd List publisher and exhibitions group Informa is still on track to hit forecasts this year. In a very brief statement, the group, which ended its interested in buying German publisher Springer earlier this month, said that further to the trading statement released on 17 November, it continues to trade in line with management expectations for the full year ending 31 December 2009. Full year results will be released on 2 March 2010.Bus and train group Go-Ahead expects interim profits from its rail business to halve though its bus business is doing better. Rail profits are expected to slide as growth in passenger numbers across its three franchises will not be sufficient to offset the reductions in net franchise subsidies from the government. Go-Ahead expects that first half operating profit will be broadly half of the first six months of last year's 34.9m. Credit lender International Personal Finance (IPF) anticipates that full year results will slightly exceed expectations. 'IPF continues to make good progress and with three significant weeks of trading to go before the year end including the key Christmas period, we expect that if present trends continue the Group's full year results will slightly exceed expectations,' the group said in a short statement.